Simple Question about Resultant Force and Direction in Statics

  • Thread starter Thread starter Marioqwe
  • Start date Start date
  • Tags Tags
    Statics
Click For Summary
SUMMARY

The discussion revolves around calculating the resultant force and its direction using the law of cosines and law of sines. The user initially calculated a resultant force of 139.1 lb and an angle of 113.1 degrees, while the textbook states the angle should be 67 degrees. The discrepancy arises from the convention of measuring angles from the horizontal axis. The correct angle, when measured appropriately, is indeed 67.0 degrees, which aligns with the significant figures presented in the textbook.

PREREQUISITES
  • Understanding of vector addition in physics
  • Familiarity with the law of cosines
  • Knowledge of the law of sines
  • Basic principles of significant figures in measurements
NEXT STEPS
  • Study vector addition techniques in statics
  • Learn more about the law of cosines and its applications
  • Explore the law of sines for solving triangles
  • Review significant figures and their importance in scientific calculations
USEFUL FOR

Students studying statics, physics enthusiasts, and anyone looking to improve their understanding of vector forces and angle measurements in engineering contexts.

Marioqwe
Messages
65
Reaction score
4

Homework Statement


http://img11.imageshack.us/f/screenshot20110117at120.png/

The question is 2.3


Homework Equations


Law of cosines and law of sines.


The Attempt at a Solution



I used the law of cosines to find the resultant force. It is 139.1 lb. However, I get 113.1 degree for the direction of the resultant force. The textbook says that it is 67 degrees. I noticed that I get 67 degrees if I subtract 139.1 from 180 degrees. Why is this? Also, I am a little confused about significant figures. Why are they giving only two sig figs for the direction?

Thanks
 
Physics news on Phys.org
Marioqwe: Usually you give the vector direction measured from a horizontal axis. Try that. They might be listing only two significant digits because the question asks you to determine the answer graphically, which is a less precise method than a calculator. Anyway, the correct answer is 67.0 deg, which rounds to the same answer.
 
Thank You for your reply. It is more clear now.
 

Similar threads

Engineering Resultant Force and Direction using Parallelogram Law
  • · Replies 6 ·
Replies
6
Views
4K
Projection of Resultant Force: Why Do We Need to Add B-Component?
  • · Replies 9 ·
Replies
9
Views
5K
Finding the direction of the force knowing the mu static
  • · Replies 3 ·
Replies
3
Views
2K
Vector Addition Problem - Statics
  • · Replies 7 ·
Replies
7
Views
2K
Truss Homework: Solving for Joint Forces using Method of Joints
  • · Replies 1 ·
Replies
1
Views
1K
Horizontal Force in Bottom Member of a Truss
  • · Replies 5 ·
Replies
5
Views
3K
Uncertainty Error and Significant Figures in this Force Tables Lab
  • · Replies 4 ·
Replies
4
Views
3K
Vectors Directions: Where is this Resultant Vector Pointing?
  • · Replies 14 ·
Replies
14
Views
2K
Statics problem on the resolution of forces
  • · Replies 18 ·
Replies
18
Views
2K
Undergrad What determines the direction of static friction forces?
  • · Replies 6 ·
Replies
6
Views
2K